Borehole logging apparatus including flexible detector and weighting means



Sept. 15, 1964 J. D. BENNETT ETAL 3,149,277

BOREHOLE LOGGING APPARATUS INCLUDING FLEXIBLE DETECTOR AND WEIGHTING MEANS Filed June 4, 1959 INVENTORS JOHN D. BENNETT PRESTON E. CHANEY a FRED M. HAYES F mm United States Patent 3,149,277 ENG APPARATU lI iCl-LUD- 3ND WEEGHT- This invention relates to bore hole logging apparatus and has particular reference to electrode assemblies for electrical logging, the assemblies being of types which may be projected through jet openings in bits to effect logging of portions of bore holes therebelow.

In accordance with the applications of Mayes & ion-es, Serial No. 683,627, filed September 10, 1957, now Patent No. 3,065,494, and of Bennett, Chaney, Mayes & l ones, Serial No. 685,717, now Fatent No. 3,647,794, September 23,1957, logging methods and apparatus are provided which may be used when a drill string is in a bore hole and may be used at any time with a minimum of interruption in drilling. Improved apparatus of this same type is disclosed in the applications of Mayes & I ones, Serial No. 818,066, and of Bennett, Chaney, Jones 8: Mayes, Serial No. 818,162, filed June 4, 1959. As pointed out, in said applications, electrical logging may be effected by the use of flexible electrode assemblies supported by housings containing recording and currentsupplying apparatus, with provisions for causing electrode assemblies to enter, pass through, and then extend beyond openings in jet bits.

Various problems are encountered in using such flexible electrode assemblies. First, there is the matter of insuring that the flexible electrode assembly wdl not hang up during its descent through a drill stem. This is particularly likely to occur if the electrode assembly is of the highly flexible type, and without substantial stiffness, as discussed in the last two applications referred to above. Pipe joints are particularly likely to present obstructions which may interfere with the free downward movement of the electrode assembly. The best assurance against any interference with the downward descent of the electrode assembly is the provision of means associated with the housing which supports the assembly adapted to slow down the descent of the housing, so that the electrode assembly may not be overtaken by the housing and will remain in substantially straight condition, having ample opportunity for its lower end to become disengaged from pipe jo nts which may temporarily impede its descent.

The second problem involved is that of insuring that the electrode assembly properly enters a jet bit opening. Flow of mud may be relied upon to enable the electrode assembly to find the opening and pass therethrough, but at the time of approach to the jet opening and entry the logging apparatus should be descending rather slowly and this end may be achieved by retarding the downward movement of the housing, for example, by causing specifl retarding of downward movement as the housing enters and passes through the drill collar above the bit. Drill collar dimensions are chosen so that entry of the housing into the drill collar precedes the attainment by the lower end of the electrode assembly of its position to enter a jet opening.

Following entry of the electrode assembly into the jet opening and passage below the same it is necessary to insure that the electrode assembly will not be held up by penetration of mud at the walls of the bore or by rock ledges therein. Continued retarding of the descent together with the use of a highly flexible electrode assembly aids in securing uninterrupted downward movement through the open portion of the hole below the bit.

3,149,277. Patented Sept. 15, 1964 While the foregoing discussion of problems is particularly directed to operations in which the assembly of the electrode assembly and apparatus housing is dropped freely through the drill stem, similar problems arise even if the logging apparatus is supported by a wire line. This last type of operation gives surface control over speeds of descent, but it is still desirable to use an electrode assembly which has a minimum chance of being held up during its descent both through the drill stern and through the portion of the hole below the bit, and which is particularly well adapted to enter a jet bit opening.

Furthermore, even if logging is to be elfected through the use of an electrode assembly supported by a cable having conductors running to the surface Where currentsupplying and recording apparatus is located, it is still desirable to provide an electrode assembly having the characteristics just noted.

The general object of the present invention relates to a type of electrode assembly which is particularly unlikely to become arrested during passage through the drill stem and therebelow, and which is well adapted to pass through a jet bit opening under the action of mud flow.

An electrode assembly of the type herein described and claimed is disclosed in the last two applications referred to above.

The general object of the nvention and other objects particularly relating to detafls of construction and operaticn will become apparent from the following description read in conjunction with the accompanying drawing, in which:

FTGURE 1A is a vertical section of the lower portion of an apparatus showing in elevation the upper portion of a preferred electrode assembly;

PEG- IRE 1B is a continuation of the electrode assembly shown in i IGURE 1A;

FIGURE 2 is a sectional view similar to FIGURE 1B but showing an alternative weighting arrangement provided at the lower end of an electrode assembly; and

FIGURE 3 is a sectional view illustrating an arrangement for providing additional weight to maintain an electrode assembly in extended condition during its descent through a drill stem.

In the present disclosure, details of power-supplying and recording apparatus and of electrode construction are not illustrated since they do not form essential parts of the invention claimed herein, and reference may be made to the applications referred to above for showings of such detafls.

Referring first to FIGURES 1A and 13, there is indicated at 2 a housing which contains power-supplying and recording apparatus which may be as disclosed in detail in the last two applications mentioned above. This housiru is provided with the lower closure plug 4 which in turn supports an electrode assembly supporting means indicated at 6, the electrode assembly proper comprising an adaptor portion 8 and the flexible cable 10 on which are provided flexible electrodes 12, 114 and 16 which may individually be of the type shown in the last two applications referred to above. These electrodes are connected by individual conductors extending through the electrode assembly cable to the apparatus within the housing. The cable forming the electrode assembly is desirably highly flexible. It will be understood, however, that various aspects of the invention are also applicable to electrode assemblies which have substantial stiffness and are, accordingly, susceptible totransrnission of compressive forces from above.

Below the electrode 12 the electrode assembly cable supports an adaptor 18 secured, for example by threading, to the uppermost element 29 of a weighting assembly. Depending from the member is a flexible wire cable 22 terminating in a stop member 28, there being strung on the cable 22 a series of lead weights 24 with rounded upper and lower ends with interposition between pairs of these weights of flexible washers 26, for example, of neoprene. A suflicient number of the weights is used to insure that during lowering the flexible electrode assembly will remain under tension. The arrangement just described provides the necessary flexibility to enable the entire assemblyto pass through jet bit openings. At the same time, there is provided an arrangement which cannot hang up on tool joints or on rock shelves in the wall of the hole below the bit. The washers 26 maintain the outside diameter of the weighting assembly to prevent engagement of the depressions between the weights from being arrested by the lower edges of the jet openings during rise or removal of the electrode assembly. A flexible strip 32 of leather or plastic is secured in a member 30 connected to the stop member 28 and facilitates, by its entrainment in the mud flow, the guidance of the electrode assembly into a jet opening in the bit.

If desired, some or all of the metal weights 24 may be used to constitute the lowermost electrode of the assembly through the use of conductive connections thereto.

FIGURE 2 shows an alternative weighting arrangement which may be used in place of the type just described. In this case a coupling member 26), corresponding to 29 in FIGURE 1B is connected to an upper closure member 34 to which a tube of thin flexible and wear resisting material such as Teflon is secured by a binding arrangement of wire or cord 38. The tube 36 is bound at intervals as indicated at 42 to provide pockets for lead shot as indicated at 49 or for containing mercury if even greater flexibility is desired. Any desired number of such pockets may be provided, the lowermost being closed by binding at 44 upon a lower closure member 46 to which may be attached a flexible strip 32' of leather or plastic corresponding to the strip 32 previously described. A highly flexible structure is thus secured capable of being readily deflected to pass into, through and then out of a jet bit opening, the pockets being in themselves flexible to yield and prevent any arresting engagement with shoulders or other obstructions.

To insure that the electrode assembly is fully extended during its descent through a drill stem it is desirable to weight its lower end as much as possible, and this result, together with centralization of its lower end during descent through the drill stem may be secured by the arrangement illustrated in FIGURE 3. In this figure, the flexible electrode cable is indicated at 48 and carries electrodes one of which is indicated at 50. Below this, the lower end of the cable is shown as secured to a weighting arrangement 52 of the type illustrated in FIG- URE 2, terminating in the flexible strip 54. A somewhat enlarged collar is provided at 56 to limit downward movement relative to the electrode assembly of a heavy hollow weight 58 which may be formed of lead, or steel jacketed lead, and is hollow and provided with extra mud passages 60 and 62 to offer minimum impedance to the flow of mud. Downward movement of the weight 58 is limited by a stop washer 68 which may be located in the joint between the drill collar 64 and the bit 66 which is shown as provided with jet openings 70. p

All of the arrangements described provide for weighted extension of the flexible electrode assembly during lowering thereof through the drill stem. In the case of FIG- URE 1 the weights are desirably of such lengths that they cannot buckle in the drill stem, having lengths at least somewhat in excess of the inside diameter of the drill stem opening. In all arrangements the weighting means (except for the weight 58) have a flexible assembly structure so that they may pass freely through jet openings of bits. In the case of the arrangement shown in FIGURE 3 the weight 58 has its weighting function operative until the lower end of the electrode assembly is either within or closely approaching the jet opening of a bit. Thereupon it is arrested by the collar or washer 68, and the cable of the electrode assembly is free to move downwardly therethrough during its extension below the bit.

It will be evident that, as indicated above, the electrode assemblies which have been described may be used even if logging is eifected by means of an electrode assembly connected to the surface by a conducting cable, recording and power-supplying devices being located at the surface. It will be understood that the logging may be carried out either by raising or lowering the drill stem, by raising or lowering an assembly of apparatus with an electrode assembly while the drill stem remains stationary, the electrode assembly being lowered or raised through a jet bit opening to log portions of the hole below the bit, or in the case of use of a conducting cable, by raising or lowering the electrode assembly while the drill stem remains stationary with the bit sufliciently raised from the bottom of the hole.

While reference has been particularly made to electrical logging utilizing electrodes, it will be evident that the guidance functions of the devices disclosed may also be used during other types of logging in which detecting elements may be located in or associated witha flexible member arranged to be projected and moved through a jet bit opening.

It will be clear that various changes in details may be made without departing from the invention as defined in the following claims.

What is claimed is:

l. A logging assembly comprising a flexible member, said member being sufliciently flexible to pass through an opening in a bit, flexible detector means carried by said member for passing through such opening and detecting signals indicative of characteristics of formations penetrated by a bore hole, and a flexible weighting assembly carried by the lower end of said member below said detector means, said weighting assembly comprising a plurality of weighting elements mounted axially end to end in closely spaced relation, and means interconnecting said weighting elements for angular deflections relative to each other.

2. A logging assembly comprising a flexible member, said member being sufliciently flexible to pass through an opening in a bit, detector means carried by said member for passing through such opening and detecting signals indicative of characteristics of formations penetrated by a bore hole, and a flexible weighting assembly carried by the lower end of said member, said weighting assembly comprising a plurality of weighting elements, means interconnecting said elements for angular deflections relative to each other, and spacer elements inter positioned between said Weighting elements, the diameters of said spacer and weighting elements being substantially equal.

3. The assembly according to claim 2 in which said weighting elements are individually rigid.

4. An assembly according to claim 2 in which said weighting elements are in the form of flexible enclosures filled with heavy free flowing solid material.

5. An assembly according to claim 4 in which said heavy material is provided by shot.

6. A logging assembly comprising an elongated flexible member, said member being sufliciently flexible to pass through a drill stem and through a non-axial aperture in a drill bit, detector means carried by said member for passing through said aperture and detecting signals indicative of characteristics of formations existing below said bit, and two part weighting means connected to the lower end of said member, said weighting means including a first part slidably mounted on said member and projecting radially therefrom so as to have its downward movement arrested by collar means within the drill stem, said first part having an opening through which said flexible member may pass downwardly upon the arrest of the downward movement of said first part, said weighting means further including a second part connected to said member for pulling said member below the position whereat said first part is arrested.

7. A logging assembly comprising an elongated flexible member, said member bein sufficiently flexible to pass through a drill stem and through a non-axial aperture in a drill bit, detector means carried by said member for passing through said aperture and detecting signals indicative of characteristics of formations existing below said bit, two part weighting means connecting to the lower end of said member, said weighting means including a first part slidably mounted on said member and projecting radially therefrom so as to have its downward movement arrested by radially extending shoulder means within the drill stem, said first part having an opening through which said flexible member may pass downwardly upon the arrest of the downward movement of said first part, said weighting means further including a second part connected to said member for pulling said member below the position whereat said first part is arrested, and guide means connected to the lower end of said weighting means, said guide means weighing much less than said weighting means and being flexible so as to be readily entrained in the flow of drilling fluid and thus serving to guide said weighting means into said non-axial aperture.

8. A logging assembly comprising a flexible member, said member being sufiiciently flexible to pass through a non-axial opening in a bit, detector means carried by said member for passing through said opening and detecting signals indicative of characteristics of formations penetrated by a bore hole, a freely flexible weighting assembly carried by the lower end of said member, and guide means carried by the lower end of said weighting assembly, said guide means weighing much less than said weighting assembly and being flexible so as to be readily entrained in the flow of drilling fluid and thereby serve to guide said weighting assembly into said non-axial opening in said bit.

9. The assembly according to claim 8 in which said guide means includes a flexible strip.

References Cited in the file of this patent UNITED STATES PATENTS 893,761 Tracy July 21, 1908 1,061,119 PPool May 6, 1913 1,826,961 Slichter Oct. 13, 1931 2,072,912 McDermott Feb. 16, 1937 2,281,766 Hawley May 5, 1942 2,653,294 McMillan Sept. 22, 1953 

1. A LOGGING ASSEMBLY COMPRISING A FLEXIBLE MEMBER, SAID MEMBER BEING SUFFICIENTLY FLEXIBLE TO PASS THROUGH AN OPENING IN A BIT, FLEXIBLE DETECTOR MEANS CARRIED BY SAID MEMBER FOR PASSING THROUGH SUCH OPENING AND DETECTING SIGNALS INDICATIVE OF CHARACTERISTICS OF FORMATIONS PENETRATED BY A BORE HOLE, AND A FLEXIBLE WEIGHTING ASSEMBLY CARRIED BY THE LOWER END OF SAID MEMBER BELOW SAID DETECTOR MEANS, SAID WEIGHTING ASSEMBLY COMPRISING A PLURALITY OF WEIGHTING ELEMENTS MOUNTED AXIALLY END TO END IN CLOSELY SPACED RELATION, AND MEANS INTERCONNECTING SAID WEIGHTING ELEMENTS FOR ANGULAR DEFLECTIONS RELATIVE TO EACH OTHER. 